PHP OOP抽象类子类注册

Question

I have an abstract question for you.

Question: How can a subclass that extends an abstract class register itself to the abstract class or another class?

Problem: Guess we have a module master named ModuleMaster and maybe someone else writes another modules to handle a specific problem without modifying the master class and named it ModuleA. For that reason we want to implement a dynamic loading of problem solutions.

My idea:

File: Extensions.php:

namespace Project\Extensions;

class Extensions
{
    public function getLoadedModules()
    {
        var_dump(ModuleMaster::LOADED_MODULES);
    }
}

File: Modules\ModuleMaster.php:

namespace Project\Extensions\Modules;

abtract class ModuleMaster
{
    public const LOADED_MODULES = array();
}

File: Modules\ModuleA.php:

namespace Project\Extensions\Modules;

class ModuleA extends ModuleMaster
{
}

I hope you understand what I mean and can help with that abstract problem.

Answer 1

This is very strange to use. It's probably a better design to have an external registry for your module. But I think you're asking for this:

File: Extensions.php:

namespace Project\Extensions;
use \Project\Extensions\Modules\ModuleMaster;

class Extensions
{
    public function getLoadedModules()
    {
        var_dump(ModuleMaster::getLoadedModules());
    }
}

File: Modules\ModuleMaster.php:

namespace Project\Extensions\Modules;

abstract class ModuleMaster
{
        public static function getLoadedModules() {
                $parent = self::class;
                return array_values(array_filter(\get_declared_classes(), function ($class) use ($parent) {
                        return in_array($parent, class_parents($class));
                }));
        }
}

File: Modules\ModuleA.php:

namespace Project\Extensions\Modules;
use \Project\Extensions\Modules\ModuleMaster;

class ModuleA extends ModuleMaster
{
}

Example use:

$e = new \Project\Extensions\Extensions;
$e->getLoadedModules();

Example result:

array(1) {
  [0]=>
  string(34) "Project\Extensions\Modules\ModuleA"
}

Please note that the code only works if all your class files are included into the context before running getLoadedModules(). PHP won't know your class exists if it is not already loaded into the context.